PWM Inverter circuit with charger using a single transformer. The circuit is based on SG3524 IC.
Inverters are electronic devices which converts battery power (DC) to alternating current (AC) which is clean enough to power our useful appliances.
Inverters can be expensive but going through this tutorial can give you enough ideas to build your own solar inverter at home without spending much.
Let’s go through the designing and construction of 100W to 6000W single phase PWM inverter or UPS with charger using a single transformer, since two transformer systems requires much money and also much space.
The PWM inverter circuit is made up of three sections:
1. Oscillator section
2. Power driver stage
3. Change over and charging stage
Credits to Nick_Zouein of instructables.com who provided the driver stage. which was later updated by me base on testing.
This is the heart of the solar inverter design. The main inverting work is done by this section using pulse width modulation IC (SG3524 or KA3524) or similar. Below is a 12V inverter circuit but few components can be changed or added to work for 24V, 48V and 96V systems whiles the concept still remains unchanged.
In this design the oscillator section is powered by a nine volts regulator IC (LM7809) when switch S1 is closed. The output frequency of the inverter is determined by R22, R23 and U12 (104 fixed cap). Theoretically, total resistance values should be higher but practically these values works best without humming in inductive loads such as fans. The output of the inverter/UPS is regulated using U3 which is 10K variable resistor or pot. This ensure that the output is always stable or within accepted range when loaded.
This stage switches the transformer on/off 50 times is a second. That is 50Hz frequency base on the output from pin 11 and 14 of SG3524.
The main components used here are N-Channel mosfets connected in parallel to deliver the required current to the transformer as shown in the circuit. In my designs I always assume that each pair will switch 20A of DC current. So if I want to switch 1000W using 12V DC supply, I calculate the max current to switch, which is 1000/12 = 83.3A. I then divide 83.3 by 20A which is my assumed current for each pair of mosfets and get 4pairs as the number of Fets to use.
Another great function of this section is to act as a half bridge rectifier during charging. During inverter charging, pin 10 of SG3524 receives positive signal from optocoupler U17 and shut down the SG causing the mosfets to turn off. The internal body diode of the mosfets then acts as rectifier to achieve DC battery charging.
Battery charging is controlled automatically by LM358. It is configured such that the output pin 1 goes high when the battery voltage drops from a set value using U19. The high output turns Q10 on, but since Q10 and Q11 are connected to form an AND gate, when optocoupler U16 senses the presence of 220V input, Q11 also turns on and relay U14 switches and charging begins. When the battery is full adjust U19 until the relay switches and the full indicator turns on to set battery full.
Relay U15 provides output from the inverter as well as your nation grid for the inverter to work as UPS. Output is filtered using 335 by 400V capacitor. In some cases without filter some inductive loads will not run. The system is protected from power surge using NTC 8 ohms or better. You can add NTC in parallel when handling higher wattage. this will cause the NTC not to over heat.
The transformer secondary coil must be Thick enough to handle the high current at the DC side else undue voltage drop will occur when loaded with little load. A center tap transformer is to be used for this project with the following specifications:
SECONDARY: 12-0-12
24-0-24
48-0-48
PRIMARY: 0-220-250
0-110-140 for US
NB: use 0-200-250 secondary for places with low line voltages else charging won’t occur.
AWG for primary should be 11 and below depending on the wattage. (You can double AWG or use higher voltage design for high output power)
NB. You can lower or increase charging current by reducing the secondary turns and voltage. E.g. To lower 12-0-12 charging current…make it 11-0-11 and vice versa.
Feedback winding: this should be a separate winding on the same transformer in the range of 12V to 16v. Winding gauge should be smaller…AWG…..18 to 28.
Inverters are electronic devices which converts battery power (DC) to alternating current (AC) which is clean enough to power our useful appliances.
Inverters can be expensive but going through this tutorial can give you enough ideas to build your own solar inverter at home without spending much.
Let’s go through the designing and construction of 100W to 6000W single phase PWM inverter or UPS with charger using a single transformer, since two transformer systems requires much money and also much space.
The PWM inverter circuit is made up of three sections:
1. Oscillator section
2. Power driver stage
3. Change over and charging stage
THE OSCILLATOR STAGE
FOR PWM INVERTER CIRCUIT WITH CHARGER
Credits to Nick_Zouein of instructables.com who provided the driver stage. which was later updated by me base on testing.
This is the heart of the solar inverter design. The main inverting work is done by this section using pulse width modulation IC (SG3524 or KA3524) or similar. Below is a 12V inverter circuit but few components can be changed or added to work for 24V, 48V and 96V systems whiles the concept still remains unchanged.
In this design the oscillator section is powered by a nine volts regulator IC (LM7809) when switch S1 is closed. The output frequency of the inverter is determined by R22, R23 and U12 (104 fixed cap). Theoretically, total resistance values should be higher but practically these values works best without humming in inductive loads such as fans. The output of the inverter/UPS is regulated using U3 which is 10K variable resistor or pot. This ensure that the output is always stable or within accepted range when loaded.
POWER DRIVE STAGE FOR PWM INVERTER CIRCUIT WITH CHARGER
This stage switches the transformer on/off 50 times is a second. That is 50Hz frequency base on the output from pin 11 and 14 of SG3524. The main components used here are N-Channel mosfets connected in parallel to deliver the required current to the transformer as shown in the circuit. In my designs I always assume that each pair will switch 20A of DC current. So if I want to switch 1000W using 12V DC supply, I calculate the max current to switch, which is 1000/12 = 83.3A. I then divide 83.3 by 20A which is my assumed current for each pair of mosfets and get 4pairs as the number of Fets to use.
Another great function of this section is to act as a half bridge rectifier during charging. During inverter charging, pin 10 of SG3524 receives positive signal from optocoupler U17 and shut down the SG causing the mosfets to turn off. The internal body diode of the mosfets then acts as rectifier to achieve DC battery charging.
PWM Inverter circuit with charger
INVERTER CHARGING
Battery charging is controlled automatically by LM358. It is configured such that the output pin 1 goes high when the battery voltage drops from a set value using U19. The high output turns Q10 on, but since Q10 and Q11 are connected to form an AND gate, when optocoupler U16 senses the presence of 220V input, Q11 also turns on and relay U14 switches and charging begins. When the battery is full adjust U19 until the relay switches and the full indicator turns on to set battery full.
Relay U15 provides output from the inverter as well as your nation grid for the inverter to work as UPS. Output is filtered using 335 by 400V capacitor. In some cases without filter some inductive loads will not run. The system is protected from power surge using NTC 8 ohms or better. You can add NTC in parallel when handling higher wattage. this will cause the NTC not to over heat.
How to wind PWM Inverter Transformer
SECONDARY: 12-0-12
24-0-24
48-0-48
PRIMARY: 0-220-250
0-110-140 for US
NB: use 0-200-250 secondary for places with low line voltages else charging won’t occur.
AWG for primary should be 11 and below depending on the wattage. (You can double AWG or use higher voltage design for high output power)
NB. You can lower or increase charging current by reducing the secondary turns and voltage. E.g. To lower 12-0-12 charging current…make it 11-0-11 and vice versa.
Feedback winding: this should be a separate winding on the same transformer in the range of 12V to 16v. Winding gauge should be smaller…AWG…..18 to 28.
Pls the circuit is not clear enough after downloading, pls can u send or post a clear image, and also can I get a video tutorials from you,
ReplyDeletePls sir am a physics student based on electrical/electronic which I like to work on circuits and I have been searching online for tutorials and video, and I come across you website which is 100% helpful
And to this am making you a mentor in circuits
Which I will be looking up to you for any help
The circuit is clear. It depends on the device you are viewing on and how it was downloaded. Check your browser image settings
DeleteHi, nice work bro!! Am trying to built 3000watts 24v inverter this circuit. Do I need to increases the range of the components in the oscillator section? Or is it on the power drive stage that needs increase in MOSFET and resistor
ReplyDeleteOnly increase the number of mosfets
DeleteCan the circuit do load cutoff, overload cutoff, and load protection.. if so is it modified sine wave of pure sine wave. Cause am trying to build 3000 watt 24v inverter
ReplyDelete1. The circuit is a modified sine wave
Delete2. overload circuit not included. check from this link
https://manycircuits.blogspot.com/2017/05/overload-protection-circuit-and-low.html
Great job, Mr Opanin, I will like to build the same circuit, but I need pcb layout of the circuit... thanks.
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Good morning Engineer. Weldon. I just designed the oscillator section of this circuit and it works well. The frequency is between 50Hz and 51Hz. And the output is okay too.
ReplyDeleteThat's my positive feedback Sir, Weldon.
In addition, I want to ask that "what are the components to be change in other to make the circuit 24V and 48V"?
I will really appreciate your positive answer on this, thanks.
Thanks Mr Opins for this lecture.
ReplyDeleteGood morning sir I HV a question about inverter transformer if the guage is not thick enough what will be result sir?
ReplyDeleteIt will limit current flow and cannot give you your desired output.
DeleteOutput regulation will also be affected when when load is connected.
The circuit is very good
ReplyDeletebut is there any way to control the charging current
It is highly expected for a positive reply
Either reduce the number of turns for the secondary or make a multi taped primary so that you will select the tap that gives you your desired current.
DeletePrimary taps can be 210V, 220v, 230v, 240v, 250V.
Note: during charging, you can select 250V tap for the least current and 210 for the highest current
Hi Sir, infact am using this inverter circiut idea now without the 335/400v cap. and its working fine. which value cap value can i use to replace it for high performance?
ReplyDelete(1) 3.3ufx400V which is same as 335x 400v
Delete(2) 4.7uf x400V which is same as 475 x400v
You can also parallel low UF capacitors provided the voltage is above 350v